CD4 and severe combined immunodeficiency: An animal experiment has demonstrated the intestinal permeability, bacterial translocation, and proinflammatory cytokines such as interferon-γ (IFN-γ) are significantly increased by stress stimulation in C57BL/6 J mice, but not in the severe combined immunodeficiency (SCID) and IFN-γ-deficient mice [40], indicating that the stress-induced intestinal barrier dysfunction depends on the presence of CD4 + T lymphocytes and IFN-γ.